Lapping article



Aug. 24, 1965 J. Y. SNYDER 3,201,905

LAPPING ART I OLE Filed May 2, 1962 36 3 FIG. 3 38' "7 ///X 24 1 56 John Y Snyder L INVENTOR BY g AT TORN EYS United States Patent 3,201,905 LAPPING ARTICLE John Y. Snyder, New Orleans, La., assignor of five percent to James H. Drury, five percent to Casimir M. Bernard, five percent to Rapier, Barre & Rapier, a firm, one and one-fourth percent to Mrs. L. C. Lehman, one and onefourth percent to L. C. Lehman, and five percent to Jake Polito, all of New Orleans, and ten and one-half percent to Millard P. Snyder, Shreveport, La.

Filed May 2, 1962, Ser. No. 191,834 1 Claim. ((Il. 51358) This invention relates to the art of lapping, and more particularly it relates to an article used to accomplish such lapping.

As used herein, the term lapping is intended to comprehend an actual lapping operation itself, as well as the closely related operations of abrading, polishing and grinding. Such lapping operations are generally carried out on a lapping machine having an article therein which rotates relative to the workpiece being lapped. There are in the prior art, many forms of lapping articles for use in such lapping machines, but none of these prior art lapping articles was able to impart the necessary flatness to the workpiece being lapped, while at the same time operating with a relatively rapid speed of production. In other words, with such prior art lapping articles, the production speed had to be quite slow if the workpiece produced was to have the desired flatness. If it was attempted to speed up the rate of lapping to a rate which was commercially acceptable for mass-production techniques, it was found that the workpieces produced did not have the necessary degree of flatness. Another drawback with the lapping articles of the prior art was the fact that the facing layer upon such articles tended to rapidly wear away during operation or to deform, the former necessitating the need for constantly replacing the facing layer and the latter tending to create a finished workpiece which did not meet the necessary flatness requirements.

With the foregoing matter in mind, it is, therefore, an object of the present invention to overcome the difficulties and deficiencies associated with prior art forms of lapping articles and to provide in their stead, an improved lapping article.

Another object of the present invention is to provide a lapping article which will produce workpieces having a high degree of flatness and which can produce such workpieces with a relatively great speed.

Another object of the present invention is to provide a lapping article having a facing sheet which will neither wear away nor deform during the normal lapping operation.

Another object of the present invention is to provide a lapping article which is simple in construction, which is inexpensive to produce, and which can operate for extended periods of time at relatively high speeds.

Another object of the present invention is to provide a lapping article which can cooperate with an abrasive material to provide a finished lapped workpiece having a high degree of flatness.

Other objects, advantages and salient features of the present invention will be apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment thereof.

Referring to the drawings:

FIGURE 1 is a top plan view of a lapping article in accordance with the principles of the present invention;

FIGURE 2 is a transverse sectional view taken along line 22 of FIGURE 1; and

FIGURE 3 is a transverse sectional view, similar to "ice FIGURE 2 but illustrating a modified embodiment of the present invention.

In general, the present invention provides a lapping article generally designated 20 which includes a back-up member generally designated 22 having a facing sheet generally designated 24 thereon.

The back-up member is a firm flat disc formed of metal or other suitable material and having a circular configuration, as can best be seen in FIGURE 1. The backup member 22 has a pair of generally parallel flat surfaces 26 and 28. A collar 30 having an adjustable screw 32 therein is provided to thereby enable the lapping article 20 to be secured to the rotating post of a lapping machine.

The facing sheet 24 is fabricated of polyethylene having a uniform thickness throughout. Such a sheet has flat, planar surfaces, nominally referred to as upper and lower surfaces, and which are respectively identified in FIGURE 2 as 34 and 36. The lower surface 36 of the facing sheet is fixed directly to the surface 28 of the backup member. The facing sheet 24 is also of a circular configuration, and as can be seen from the drawings, has a diameter at its lower surface which is substantially equal to the diameter of the back-up member 22.

Preferably, the edge of the facing sheet 24 is beveled or otherwise angularly relieved to permit the workpiece to pass across the edges of the lapping article without being scratched. To this end, a bevel edge 38 is formed on the facing sheet, with such bevel edge extending upwardly and inwardly from the lower surface 36 to the upper surface 34. Stated in another way, the outer edge 38 of the facing sheet upper surface 34 is relieved below the plane of the central portion of the sheet upper surface 34.

When the lapping article 20 of the present invention is attached to a lapping machine, and is provided with suitable fluid, paste, or other abrasive material, it is able to accomplish a suitable lapping operation to impart a high degree of flatness to a workpiece being lapped. The lapping article 20 is rotated by the lapping machine and the facing sheet 24 contacts and laps, abrades and otherwise machines the surface of the workpiece beneath it. The surface 36 on the back-up member 22 is preferably a highly accurate flat surface, and thus the uniform thickness facing sheet 24 which is secured to that surface not only takes the wear during the lapping operation, but also transfers the precision flatness of the surface 36 to the surface of the workpiece being lapped. Even if a slight variation or unevenness were present on the surface 36 of the back-up member, this could be compensated for by the sheet 24 which is itself of a uniform thickness and of a relatively soft, pliable nature, due to the characteristics of the polyethylene material. Such polyethylene material also resists any tendency to wear,

deform or flow during the lapping operation, and thus presents a facing sheet which can be used for extended durations of time and which produces a workpiece having a high degree of flatness.

In FIGURE 3, a modified embodiment of the present invention is shown wherein a second polyethylene sheet 24 having an upper surface 34', a lower surface 36 and a beveled or relieved edge 38 is secured on top of the facing sheet 24. As shown, the upper surface 34 of the facing sheet 24 and the lower surface 36 of the facing sheet 24' are adhered directly to one another. Since the sheets 24 and 24 are superposed the beveled edge 38 may extend inwardly somewhat beneath the lower surface 36 of the sheet 24'. In this manner, the outer edge of the upper sheet 24' may be deformed even further downwardly during operation by having the lower edge 36 thereof deform into contact withthe edge 38 of the lower sheet '24. The provision of two polyethylene fac-' ing sheets as shown in this embodiment increases the effective life of the lapping articlesstill further, since a flatness of the workpiece being produced ismaintained;

After reading the foregoing detailed description, it will be apparent that the objects set=forth at the outset of the specification have been successfully achieved, Accordingly, what is claimed is: V

An article for lapping usinga fluid or, paste abrasive comprising a firm'flat back-up member and at least one separate polyethylene facing sheet of uniform thickness fixed directly on said member, said sheet and saidrnember being circular, said sheet upper surface at itsouter edge being relieved below the plane of said sheet upper surface. 4

References Cited by the Examiner UNITED STATES PATENTS MacLean 51-195 Bogdanfiy 5128l Graft 5ll95 Maynardet a1. 5ll3l Robinson 2 5l13l X Schenk 5ll3l Hicks 51209.1 X Roshong etal. 51l3l Porteret al. 51l31 Danec 51-309 Galey 15230.16 Blackrner e 51-309 Mushrush 5l281 Foland 1 5l'-1'95 Olton 51--195 20 LESTER M. SWINGLE,Primary Examiner. 

